Obama defended his intervention, saying, “I'm not coming here to fix any votes.”

He told a joint news conference with British Prime Minister David Cameron on Friday: “I'm not casting a vote myself. I'm offering my opinion. And in democracies, everybody should want more information, not less, and you shouldn't be afraid to hear an argument being made. That's not a threat.”

The president also responded to Johnson's accusation that Obama, whose father was from Kenya, a former British colony, harbored an "ancestral dislike of the British empire."

Obama answered by saying that a second bust of Churchill sat outside his second-floor office, where he sees it every day.

His intervention was welcomed by Cameron and others. Former British ambassador to the U.S., Christopher Meyer, tweeted: "Obama only restated what the US has already told us. A bilateral trade deal will take second place to finishing TTIP negotiations e.g. 2020."

Obama only restated what the US has already told us. A bilateral trade deal will take second place to finishing TTIP negotiations e.g. 2020.

On Saturday, Obama played golf after answering questions from young Britons at a town hall event, and toured London’s historic Globe theater, which is marking the 400th anniversary of Shakespeare's death.